WASHINGTON — U.S. jets and armed drones conducted four more airstrikes against Islamic State positions in northern Iraq on Saturday as President Barack Obama said the American air campaign would not expand beyond the limited objectives he has outlined.

All of the air attacks took place in the area of Sinjar, in the northwest part of the country, where militants have surrounded and threatened to kill as many as 40,000 members of the minority Yazidi sect.

The U.S. Central Command said that the strikes, which took place in the late morning and midafternoon Eastern time, had destroyed several armored personnel carriers and armed trucks. “All aircraft safely exited the area,” it said.

The ongoing strikes, which began Friday, address “immediate” concerns of protecting Americans, besieged minorities and critical infrastructure in the north, Obama said. But comprehensive aid to push back advances by the Sunni Muslim extremists through much of the country in the past two months will require a new Iraqi government, he said.

Formation of that government, already delayed beyond a constitutional deadline after elections in the spring, fell farther behind as a parliamentary vote scheduled for Sunday was postponed for a day amid internal wrangling among Shiite politicians.

Obama’s remarks put in sharp relief his decision in the past week to use airstrikes to keep Iraq from disintegrating and prevent “genocide” against minorities, while maintaining enough leverage to press for an inclusive government that he is convinced is the country’s only long-term salvation.

The administration is pushing for Iraq’s majority Shiites to choose a replacement for Prime Minister Nouri al-Maliki, whose sectarian governance has led many Iraqi Sunnis to tolerate, and sometimes support, the Sunni extremists of the Islamic State.

Asked how long the airstrikes would continue, Obama said that “the most important timetable that I’m focused on right now is the Iraqi government getting formed and finalized.”

“I don’t think we’re going to solve this problem in weeks,” he said on the White House South Lawn before departing for a two-week vacation in Martha’s Vineyard, Mass. “This is going to be a long-term project.”

“What we don’t have yet is a prime minister and a Cabinet that can … start reaching out to all the various groups and factions inside Iraq and give confidence to populations in the Sunni areas” that the militants are “not the only game in town,” he said.

“To ensure that Sunni populations reject outright these kinds of incursions,” Obama added, “they’ve got to feel like they’re invested in a broader national government. And right now, they don’t feel that.”

In a letter sent to Congress late Friday, Obama said U.S. military operations would be “limited in their scope and duration as necessary to protect American personnel” and to help Iraqi forces aid and rescue besieged minorities.

While politicians argued in Baghdad, there were signs of increasing cooperation between Iraqi security forces and the peshmerga, the military force of the Kurdish regional government.

In an unprecedented delivery Friday to Irbil, the Kurdish capital, Iraqi security forces re-supplied the peshmerga with a planeload of ammunition, U.S. defense officials said.

The Pentagon prepared Saturday for another airdrop of humanitarian supplies to the stranded Yazidis, after one Thursday and a second Friday. Obama placed calls to British Prime Minister David Cameron and French President Francois Hollande, both of whom agreed to assist the humanitarian effort.

An 18-year-old from Monument who damaged nearly $100,000 worth of art at the Denver Art Museum pleaded guilty to criminal mischief, a class four felony, in a Denver courtroom on Thursday, according to the District Attorney's Office.

Arturo Hernandez Garcia, who in 2014 became the first Colorado resident to claim sanctuary, once again faces possible expulsion from the U.S. and separation from his wife and daughters after his stay of deportation lapsed Thursday.